1. Field of the Invention
The present invention relates to the structure of a laminated core for a motor.
2. Related Art
The cores used for the rotor and stator of a motor are generally of the laminated type. The following procedural steps are taken for assembling the laminated core.
1) To laminate a preset number of core members in a state that those members are put in the same punched direction. The stuff members are made of magnetic material and are each punched to have a preset pattern by a punching machine. PA1 2) To press fit the laminated stuff members into a laminated core. PA1 3) To wash the laminated core to remove rust preventing oil. PA1 4) To form an insulating layer on a specified area on the surface of the laminated core by a powder coating method, for example. The powder coating method is generally a called electrostatic spray painting method. In this method, electrostatically charged insulation powder is sprayed over the earthed core, the insulation powder particles attached to the core are welded to form an insulating layer.
FIGS. 10 through 12 diagrammatically show the structure of a laminated core constructed through the procedural steps as just mentioned. A number of core members 56 (see FIG. 11) are placed one layer upon another to form a laminated core 50. The laminated core 50 is provided with a plural number of protruded poles 52 radially extending from the center of the core. Each of the protruded poles 52 has a circumferentially extended part 53 at the distal end thereof. In the construction of the laminated core 50, insulating layers 54 are layered on the upper and lower surfaces of the outer part of the core member 56 as viewed in the laminating direction. The insulating layer 54 is required for insulating the core from the winding wire. The insulating layer 54 is formed on the area on which the winding wire is wound, viz., the area including the entire surface of each insulating layer 54 and defining slots 58 for receiving coil.
In forming the core member 56, it is punched to have a preset pattern by a punching machine. The edge of one of the surfaces of the core member 56 is crooked by the punching process. In laminating the core members 56, those members are layered in a state that the crooked faces 59 thereof are put in the same direction as shown in FIG. 12. Then, those laminated members are driven together, and the specified areas thereof are covered with insulating layers 54.
In the construction of the laminated core 50, the core members 56 are laminated in a state that the crooked faces 59 of the core members 56, which result from the punching process, are put in the same direction. The crooked face 59 occupies an areal part of one of the surfaces, located closer to the distal end of the core member 56. A thick insulating layer (of 0.25 to 0.3 mm thick) is formed to cover the sharp edge of the crooked face 59. The formation of the thick insulating layer creates various problems. A large amount of expensive insulating material is used. The size of the core part having the winding wire placed thereon is increased. This makes it difficult to reduce the motor thickness. Since the wire is coiled on the thick insulating layer, the required wire for the winding is inevitably long. The use of a long winding wire results in an increase of the winding resistance, and a decrease of the startup torque of the motor, viz., deterioration of the motor characteristic.